1. Field of the Invention
The present invention relates to a pickup device, and more particularly to a pickup device which is used for performing recording and reproducing operations on a DVD, a CD-ROM, an MD, or the like.
2. Description of the Related Art
A pickup device of this kind comprises: a movable frame that holds a pickup; and a guide shaft that guides travelling of the movable frame in directions along which the movable frame approaches and separates from a disk table. Rotational motion of a travel driving motor is converted into linear motion of the movable frame by a pinion and rack mechanism or the like. Generally, the guide shaft is configured by a main shaft and a sub shaft which are attached to a support frame (chassis).
Such a pickup device is disclosed in Japanese Patent Unexamined Publication No. Hei. 8-36848. In the disclosed pickup device, a main shaft and a sub shaft which serve as a guide shaft are fixed in a state where end portions of the shafts are pressed by a plate face of a support frame, a perpendicular rising end face disposed on the support frame, and the head or the shaft of a head screw which is screwed into a tapped hole of the support frame.
On the other hand, it is desired to configure a pickup device of the above-mentioned kind so that a beam output from a pickup perpendicularly impinges on a recording plane of a disk which is mounted on a disk table. In order to satisfy this request, tilt adjustment must be performed by a tilt adjusting mechanism. In one of means for performing tilt adjustment, end portions of the above-mentioned main and sub shafts are vertically moved with respect to the support frame to finely adjust the tilts of the shafts. As a tilt adjusting mechanism using such means, conventionally, known is a mechanism which is schematically shown in FIG. 6.
The tilt adjusting mechanism of FIG. 6 has a structure in which a post 1 having a spiral cam groove 2 is attached to a support frame 10, and an end portion 30a of a guide shaft 30 such as a main shaft or a sub shaft is fitted into the cam groove 2, thereby holding the guide shaft. In the tilt adjusting mechanism, when the post 1 is rotated about the axis as indicated by the arrow a, the end portion 30a of the guide shaft 30 is vertically moved while being guided by the cam groove 2, whereby the tilt of the guide shaft 30 with respect to the support frame 10 can be finely adjusted so as to perform tilt adjustment.
However, the tilt adjusting mechanism shown in FIG. 6 has a problem in that the post 1 which is precisely machined must be used and hence the production cost is high. In the above-mentioned pickup device which is disclosed in Japanese Patent Unexamined Publication No. Hei. 8-36848, there is a problem in that tilt adjustment cannot be performed by means for finely adjusting the tilt of the guide shaft with respect to the support frame.
The invention has been made in view of the above problems. It is an object of the invention to provide a pickup device comprising a tilt adjusting mechanism in which means for finely adjusting a tilt of a guide shaft with respect to a support frame can be used to perform tilt adjustment, and the production cost can be easily lowered.
It is another object of the invention to provide a pickup device comprising a tilt adjusting mechanism in which tilt adjustment can be surely performed.
The pickup device of the invention comprises: a movable frame that holds a pickup; and a guide shaft that guides travelling of the movable frame in directions along which the movable frame approaches and separates from a disk table. As described at the beginning of the description, when rotational motion of a travel driving motor is converted into linear motion of the movable frame by a pinion and rack mechanism or the like, therefore, the movable frame travels in the approaching and separating directions with respect to the disk table along the guide shaft. Generally, the guide shaft is configured by a main shaft and a sub shaft which are attached to a support frame.
The pickup device of the invention comprises a tilt adjusting mechanism which can finely adjust a tilt of the guide shaft with respect to the support frame. The tilt adjusting mechanism comprises: a flat rising end face that is disposed on the support frame and that is perpendicular to a plate face of the support frame; a spring member that is held by the support frame, that is contacted at a straight tip end portion to an end portion of the guide shaft to always elastically urge the end portion of the guide shaft in an upward direction along which the end portion separates from the plate face of the support frame; a head screw including a head, the head having a downward-tapered pressing face which is contacted to the end portion of the guide shaft that is elastically urged in the upward direction by the spring member, which cooperates with the tip end portion and the rising end face of the spring member to pressingly hold the end portion of the guide shaft, and which enables the end portion of the guide shaft to be pressed down while causing the end portion to slide over the rising end face; and a tapped hole which is formed in the support frame, and into which the head screw is screwed, thereby supporting the head screw in parallel with the rising end face.
In the pickup device of the invention comprising such a tilt adjusting mechanism, the flat rising end face which perpendicularly rises from the plate face of the support frame performs a function of guiding vertical motion of the end portion of the guide shaft. When the head screw is rotated in a fastening direction (forward direction) to be screwed into the tapped hole of the support frame, the pressing face of the head of the head screw presses down the end portion of the guide shaft against the urging exerted by the spring member to downward move the end portion. In contrast, when the head screw is rotated in a loosening direction (reverse direction) to be unscrewed from the tapped hole, the end portion of the guide shaft is pushed up to be upward moved by the urging of the spring member while being contacted to the pressing face, as the pressing face is raised. Therefore, the end portion of the guide shaft is vertically moved by only rotating the head screw in the forward or reverse direction, whereby the tilt of the guide shaft with respect to the support frame is finely adjusted. In the tilt adjusting mechanism, it is not necessary to use the expensive post 1 which has been described with reference to FIG. 6.
In the pickup device of the invention, preferably, the guide shaft is configured by a main shaft and a sub shaft, a position of one end portion of the main shaft is set as a reference position, and another end portion of the main shaft and at least one of one and another end portions of the sub shaft are attached to the support frame via the tilt adjusting mechanism. In the thus configured pickup device, the other end portion of the main shaft can be vertically moved with respect to the one end portion of the main shaft which is set as the reference position, so as to finely adjust the tilt of the main shaft, and the one and/or other end portion of the sub shaft can be vertically moved so as to finely adjust the tilt of the sub shaft. Therefore, the workability of tilt adjustments of the main and sub shafts can be improved.
Preferably, the pickup device of the invention is configured so that the other end portion of the main shaft and the other end portion of the sub shaft are attached to the support frame via the tilt adjusting mechanism, the spring member has: a coil portion which is fittingly supported by an attaching piece disposed on the support frame; and a pair of the tip end portions which are respectively extended in opposite directions from a winding start and a winding end of the coil portion, one of the tip end portions is contacted to the other end portion of the main shaft, and the other of the tip end portions is contacted to the other end portion of the sub shaft. According to this configuration, the single spring member is commonly used in the tilt adjusting mechanism for attaching two shafts, i.e., the main shaft and the sub shaft to the support frame. Therefore, the number of parts is reduced and the production cost can be easily reduced.
In the tilt adjusting mechanism used in the pickup device of the invention, positional relationships among the tip end portion of the spring member, the rising end face, and the head screw may be set in one of the following manners.
In one manner, the tip end portion of the spring member straight elongates from a side of the head screw screwed into the tapped hole toward the rising end face while passing below the end portion of the guide shaft and inclined to be lowered as elongating. In the other manner, the tip end portion of the spring member straight elongates from a side of the rising end face toward the head screw screwed into the tapped hole while passing below the end portion of the guide shaft and inclined to be lowered as elongating.
In both the cases, tilt adjustment can be performed. In the latter case, or in the mechanism where the tip end portion of the spring member straight elongates from the side of the rising end face toward the head screw while passing below the end portion of the guide shaft and inclined to be lowered as elongating, particularly, the urging force of the spring member acts in the direction along which the end portion of the guide shaft is separated from the rising end face, and does not act in the direction along which the end portion is pressed against the rising end face. When the head screw is rotated in the reverse direction to raise the pressing face, therefore, there never arises a phenomenon that the end portion of the guide shaft is pressingly fixed by the tip end portion of the spring member and the rising end face and the pressing face is kept to be separated from the end portion of the guide shaft (hereinafter, such a phenomenon is referred to as xe2x80x9cblock phenomenonxe2x80x9d). This serves to improve the reliability of tilt adjustment. When the head screw is rotated in the forward direction to lower the end portion of the guide shaft, the downward-tapered pressing face disposed on the head of the head screw functions to press the end portion of the guide shaft against the rising end face, thereby increasing the frictional force exerted between the rising end face and the end portion of the guide shaft. At this time, the rotation of the head screw for lowering the end portion of the guide shaft is manually performed, and hence there never arises a situation where the increase of the frictional force causes the end portion of the guide shaft to be pressingly held and fixed by the pressing face and the rising end face.
In the former case, or in the mechanism where the tip end portion of the spring member straight elongates from the side of the head screw toward the rising end face while passing below the end portion of the guide shaft and inclined to be lowered as elongating, it is preferable to set the tilt angle of the tip end portion of the spring member with respect to the rising end face to an angle at which the end portion of the guide shaft cannot be pressingly fixed by only the tip end portion and the rising end face. According to this configuration, even when the tip end portion of the spring member straight elongates from the side of the head screw toward the rising end face while passing below the end portion of the guide shaft and inclined to be lowered as elongating, the block phenomenon does not occur.
As the head screw, a countersunk head screw may be used. In this case, the pressing face is formed by a lower face of a head of the countersunk head screw. In a countersunk head screw, the lower face of the head is inclined in a downward-tapered manner, and the lower face is inclined by 45 deg. or about 45 deg. with respect to the axis. Therefore, the function which should be performed by the pressing face, i.e., the function of xe2x80x9cpressing down the end portion of the guide shaft while causing the end portion to slide over the rising end facexe2x80x9d can be attained by the lower face of the head of the countersunk head screw.